Downhole Tool Actuation Methods

ABSTRACT

Methods for actuating tools within a wellbore include disposing the tool and an associated tool actuator within the wellbore. The tool actuator includes an amount of flammable, non-explosive material and a heating igniter. The tool actuator actuates the tool by generating gases which create a pressure differential.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates generally to methods for actuating a downhole toolusing a power charge within a wellbore.

2. Description of the Related Art

Power charges have been used to generate gases needed to applycompressive force for an affixed setting tool. A typical use for a powercharge is as the motive force for a wireline setting tool. Such asetting tool is used to set bridge plugs, cement retainers andproduction packers or other downhole devices which must be anchoredwithin a wellbore. Power charges are typically initiated by an igniterwhich uses electrical current to detonate a small amount of explosivematerial. A jet of hot burning gases created by the igniter willdetonate a secondary pellet which, in turn, initiates the setting tool.

Some conventional igniters have reliability problems. A nichrome wirewhich is in contact with black powder within the igniter tends to suffercorrosion. As a result, there can be an unacceptable failure rate forsuch igniters after one year of shelf life. These conventional ignitersare usually rated as explosive material, requiring special packaging andhandling and thus increasing costs and delivery times.

SUMMARY OF THE INVENTION

The invention provides improved systems and methods for activating orsetting a tool within a wellbore. Tool actuators are described whichinclude at least one heating igniter which is non-explosive and whichinitiates a burn of the actuator by generating a high temperature whichis sufficient to cause flammable material within the actuator to ignite.Electrical voltage is supplied to the igniter to energize it. Indescribed embodiments, electrical current is provided from the surfacevia wireline. In one embodiment, the igniter is a resistive heatingelement. In an alternative embodiments, the igniter is a coil of wire ora cartridge heater. As the flammable material within the actuator burns,it creates gases which generates an abrupt pressure differential whichis useful for actuation of a downhole tool. In some embodiments, thepressure differential will exert a compressive axial force which willactuate the downhole tool. In described embodiments, the pressuredifferential will shift a piston for tool actuation.

In accordance with described methods of use, a non-explosive heatingigniter and flammable material are incorporated into a tool actuator.The tool actuator and an associated downhole tool to be actuated arethen run into a wellbore using a running string. The running string maybe in the form of either wireline or tubing. When the tool to beactuated is at a location wherein it is desired to actuate the tool, theactuator is initiated by energizing the heating igniter therebyactuating the tool within the wellbore.

The actuator can be used to actuate (set) a wide range of types ofmechanical packers, bridge plugs, composite frac plugs and the like. Inaddition to packers and plugs, numerous other downhole tools can beactuated or operated using a power charge. Sliding sleeve devices orother tools which use linear motion for actuation can be actuated usingthe power charge. Methods are described which are useful for actuating awide variety of tools which use compressive axial force for actuation.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is madeto the following detailed description of the preferred embodiments,taken in conjunction with the accompanying drawings, wherein likereference numerals designate like or similar elements throughout theseveral figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of an exemplary wellborecontaining a packer device and packer setting tool in accordance withthe present invention.

FIG. 2 is a side, cross-sectional view of portions of the setting toolfrom FIG. 1 and related components, including a power charge inaccordance with the present invention.

FIG. 3 illustrates an exemplary power charge igniter constructed inaccordance with the present invention.

FIG. 4 illustrates an alternative embodiment for a power charge igniterconstructed in accordance with the present invention.

FIG. 5 depicts a further alternative power charge igniter constructed inaccordance with the present invention.

FIG. 6 is a side, quarter cross-sectional view of an exemplary slidingsleeve device to be actuated by a power charge igniter in accordancewith the present invention.

FIG. 7 is a side, quarter cross-sectional view of the sliding sleevedevice of claim 5 following actuation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an exemplary wellbore 10 which has been drilled throughthe earth 12 from the surface 14. The wellbore 10 is lined with metalliccasing 16. A tool string 18 is shown disposed into the wellbore 10. Thetool string 18 includes a wireline running string 20 from which issuspended a packer device 22. The packer device 22 may be acompression-set packer of a type known in the art. In the depictedembodiment, the packer device 22 includes an elastomeric packer element24 which is expanded radially to set against the casing 16 by axialcompression.

The packer device 22 is affixed to an actuator in the form of a packersetting tool 26. The packer setting tool 26 is operable to set packerdevice 22 by applying compressive force to portions of the packersetting tool 26. Except where otherwise described herein, the packersetting tool 26 can be constructed and operated in the same manner asthe E-4 packer setting device which is available commercially from BakerHughes Incorporated of Houston, Tex. However, the packer device 22 couldbe any form of mechanical packer, bridge plug, lock, composite frac plugor similar devices which are set within the wellbore 10 by applicationof compressive axial force.

FIG. 2 illustrates portions of the packer setting tool 26 in greaterdetail. The packer setting tool 26 includes an outer housing 28 whichdefines a recess 30 for retaining an actuator or power charge 32. Apiston 34 is retained within the housing 28 and is axially moveabletherein. Movement of the piston 34 with respect to the housing 28 willcause setting of the packer device 22.

The actuator/power charge 32 includes a frangible outer casing 36 whichcontains an amount of non-explosive, but flammable material 38. Theflammable material 38 may be made up using different recipes ormixtures, as is known in the art, to allow burning at various rates toallow optimum setting times for different types of packer devices. Theflammable material 38 is a material in the solid phase of matter thatcan readily undergo combustion in the source of ignition under standardcircumstances, i.e., without artificially changing variables such aspressure or density or by adding accelerants. Flammable material isreadily combustible. It may cause or contribute to fire throughfriction. Readily combustible materials can be powdered, granular orpasty chemicals which are dangerous if they can be easily ignited bybrief contact with an ignition source. Flammable material 38 is veryenergetic and produces high temperature gaseous products on combustionwhich leads to high energy density needed for producing the requiredpropulsive force. Flammable material 38 can consist of several chemicalingredients such as oxidizer, fuel, binder, plasticizer, curing agent,stabilizer and cross-linking agent. The specific chemical compositiondepends on the desired combustion characteristics for a particularapplication. The flammable material 38 may contain items such as, butnot limited to, perchlorates, nitrates, oxamides, sulfur and carboncompounds. Different chemical ingredients and their proportions resultin different physical and chemical properties, combustioncharacteristics and performance. The outer casing 36 is shaped and sizedto reside within the recess 30 in a complementary manner. A heatingigniter 40 is also contained within the casing 36 in contact with theflammable material 38. Electrical conduit 42 is interconnected with theheating igniter 40. The electrical conduit 42 will extend upwardly alongthe wireline 20 to an electrical power source 44 (FIG. 1) at surface 14.The electrical power source 44 may be a generator, battery or othersource of electrical energy which is sufficient to provide energizingpower to the heating igniter 40.

FIG. 3 illustrates an exemplary heating igniter 40 in greater detail.The depicted heating igniter 40 is a metallic resistive heating elementwhich will heat up when electrical current is applied to it. Theresistive heating element is preferably made of stainless steel.However, it might also be fashioned from a bimetallic or non-metallicmaterial or other suitable materials. In the depicted embodiment, theresistive heating element is rod shaped. However, it should beunderstood that the resistive heating element may have other shapes.When energized, the heating igniter 40 should achieve a temperature thatis sufficient to reach the ignition temperature of the flammablematerial 38. This temperature may be in the range of from about 750° F.to about 900° F. It is noted, however, that this range of temperature isexemplary only and not intended to limit the invention in any way. It isfurther noted that the ignition temperature may vary depending upon thetype and form of flammable material used, ambient pressure and otherconditions.

FIG. 4 illustrates an alternative embodiment for an igniter 40′ inaccordance with the present invention. The heating igniter 40′ is a coilof wire. Current power supplies in the field will provide about 200volts of electrical power and 1 to 1.5 amps. That power can be used forup to about 10 seconds. Wire size can be varied to provide differentwatt densities, output temperatures and the like to adjust for differentflammable material 38.

FIG. 5 depicts a further alternative embodiment for an igniter 40″ inaccordance with the present invention. The igniter 40″ is a cartridgeheater which includes a thin wire wrapped around a core. A thin coatingof epoxy or the like protects the wire from damage and shorting. Thecartridge heater igniter 40″ preferably includes a thermal fuse whichwill break electrical continuity after the cartridge heater 40″ has beenheated to the ignition temperature for a predetermined amount of time.The break in electrical continuity would signal to an operator atsurface 14 that the power charge 32 has been initiated and itsassociated downhole tool has been actuated. It is further noted thatresistive elements other than the particular constructions describedhere can be used to create heat to ignite the flammable material 38.

In an exemplary method of operation, the packer setting tool 26 andpacker device 22 are run into the wellbore 10 on wireline running string20. When the packer device 22 is at a location wherein it is desired toset the packer device 22 within the wellbore 10, the packer setting tool26 is actuated by initiating the actuator/power charge 32 within.Initiation of a burn of the actuator 32 is done by energizing theheating igniter 40, 40′ or 40″. As the flammable material 38 burns, itgenerates gas which will generate an abrupt pressure differential withinthe casing 36 and rupture the casing 36. The pressure differential willthen exert a compressive axial force upon the piston 34. Because heatingigniter 40, 40′, 40″ is non-explosive, it is believed that use of themwill provide improved safety and reduced costs.

FIGS. 6 and 7 illustrate an instance wherein a sliding sleeve tool 50 isbeing actuated using an actuator/power charge 52 which is constructedand operates in accordance with the present invention. In this instance,the running string is a string of tubing 54 rather than a wirelinerunning string, such as wireline running string 20 described previously.The tubing string 54 may be coiled tubing or conventional oilfieldtubulars which are interconnected in an end-to-end fashion, as is knownin the art. The actuator 52 is secured within a tubular actuator housing56 which includes a central bore 58 through which fluid may be flowed.The actuator housing 56 is affixed to the sliding sleeve tool 50.Electrical conduit 42 extends from the actuator 52 to an electricalpower source, such as electrical power source 44.

The sliding sleeve device 50 includes an outer housing 60 which definesa bore 62 along its length. Outer lateral flow ports 64 are disposedthrough the outer housing 60. A sliding sleeve member 66 is retainedwithin the bore 62 and includes a tubular sleeve body 68 having innerlateral flow ports 70 formed therein. The sliding sleeve member 66 isaxially moveable within the bore 62 between a first position, whereinthe inner lateral flow ports 70 are not aligned with the outer lateralflow ports 64 (FIG. 5), and a second position, wherein the inner lateralflow ports 70 are aligned with the outer lateral flow ports 64 (FIG. 7).When the sliding sleeve member 66 is in the first position, fluid flowthrough the outer lateral flow ports 64 is blocked by the sleeve body68, and when the sliding sleeve member 66 is in the second position,fluid flow through the outer lateral flow ports 64 is permitted. Whenrun into the wellbore 10, and prior to actuation, the sliding sleevemember 66 is in the first position.

The actuator 52 may be constructed and operate in generally the samemanner as the actuator 32 described previously. The piston 34 associatedwith the actuator 52 is affixed to sliding sleeve member 66 within thesliding sleeve tool 50. The sliding sleeve tool 50 is actuated byheating the heating igniter 40, 40′ or 40″ within the actuator 52 toignite its flammable material and generate gases and a resulting abruptpressure differential. The pressure differential generates compressiveforce axially downwardly upon the piston 34. Downward movement of thepiston 34 shifts the sliding sleeve member 66 from its first position toits second position, as depicted in FIG. 6.

The invention provides an actuator for a downhole tool which, in certainembodiments, generates compressive force in an axial direction. Thedownhole tools which can be actuated include any of a number of toolswhich use a pressure differential as a force for actuation. Exemplarytools which can be actuated include any form of mechanical packer,bridge plug, lock, composite frac plug or similar devices which are setwithin the wellbore 10 by application of compressive force. In otherembodiments, the tools which can be actuated include valves, such assliding sleeve valves. The valves are actuated between open and closedpositions by application of an axial compressive force which is providedby the actuator 52.

During burning of the flammable material 38, the actuator 26, 52generates gas which results in creation of a pressure differential. Asdescribed previously, the pressure differential is useful to generate acompressive axial force which will move a piston 34. However, thepressure differential might actuate a downhole tool by other methods.For example, the pressure differential might cause release of anactuating member, such as a piston, by moving a retaining member isrestraining the actuating member against movement. As a result, theactuating member moves and thus actuates the downhole tool.Alternatively, the gas pressure differential actuates may assist anotheractuating mechanism, such as use of drilling fluid pressure orhydrostatic pressure, in actuating the downhole tool.

In addition, the invention provides methods for actuating a tool withina wellbore. In accordance with the methods, a tool and an associatedtool actuator are disposed into a wellbore. Thereafter, a heatingigniter is energized with electrical power to cause ignition offlammable material within the tool actuator. Energy resulting from theignition of the flammable material will move a piston 34 to provide theapplication of compressive force used to actuate the associated downholetool.

What is claimed is:
 1. A method of actuating a downhole tool within awellbore, the method comprising: disposing the downhole tool and anassociated tool actuator into the wellbore, the tool actuator includinga power charge with a non-explosive heating igniter; and initializing aburn of the power charge by energizing the heating igniter with electricpower to create a pressure differential adapted to allow for actuationof the downhole tool.
 2. The method of claim 1 wherein the burn of thepower charge generates a pressure differential adapted to actuate thedownhole tool.
 3. The method of claim 1 wherein the actuator comprises:an outer casing; an amount of flammable material within the casing; andthe non-explosive heating igniter is retained within the casing and incontact with the flammable material, the heating igniter beingenergizable by electric power to reach a temperature sufficient toignite the flammable material.
 4. The method of claim 2 wherein thepressure differential generates a compressive axial force which moves apiston to cause the tool to be actuated.
 5. The method of claim 1wherein the tool is a mechanical packer, bridge plug, lock, compositefrac plug which is set within the wellbore by application of compressiveforce.
 6. The method of claim 1 wherein the tool is a valve which isactuated between open and closed positions by application of compressiveforce.
 7. The method of claim 3 wherein the heating igniter comprises ametallic resistive heating element, a coil of wire or a cartridgeheater.
 8. The method of claim 3 wherein the heating igniter is formedof stainless steel.
 9. The method of claim 1 wherein the flammablematerial comprises one or more of perchlorates, nitrates, oxamides,sulfur and carbon compounds.
 10. A method of actuating a tool within awellbore, the method comprising: disposing the tool and an associatedtool actuator into the wellbore, the tool actuator including a powercharge having a non-explosive heating igniter and an amount ofnon-explosive, flammable material contained within a casing; initiatingthe power charge by energizing the heating igniter with electric powerto ignite the flammable material; and ignition of the flammable materialgenerating gas to form a pressure differential which is effective toactuate the tool.
 11. The method of claim 10 wherein the heating igniteris energized by a power source which is located at a surface locationwith respect to the wellbore.
 12. The method of claim 10 wherein thetool is a mechanical packer, bridge plug, lock, composite frac plugwhich is set within the wellbore by application of compressive force.13. The method of claim 10 wherein the tool is a valve which is actuatedbetween open and closed positions by application of compressive force.14. The method of claim 10 wherein the heating igniter comprises ametallic resistive heating element, a coil of wire or a cartridgeheater.
 15. The method of claim 10 wherein the heating igniter is formedof stainless steel.